Mmio addressing using a translation lookaside buffer

ABSTRACT

A method for processing an instruction by a processor operationally connected to one or more buses comprises determining the instruction is to access an address of an address space that maps a memory and comprises a range of MMIO addresses. The method determines the address being accessed is within the range of MMIO addresses and generates, based on the determination, a first translation of the address being accessed to a bus identifier identifying one of the buses and a bus address of a bus address space. The bus address resulting from the translation is assigned to a device accessible via the identified bus. The method generates an entry in a translation lookaside buffer. A request directed to the device is sent via the identified bus to the bus address resulting from the translation.

BACKGROUND

The present disclosure relates to the field of computer systems. Moreparticularly, the present disclosure relates to processing aninstruction by a processor.

When processing instructions by a processor, often communication withperipheral devices, e.g., input/output devices or memory devices, isrequired. Such communication may require an identification of the targetdevice and/or addresses assigned to the target device. Different methodsfor enabling such a communication are known. Considering modern computersystems, the communication with peripheral devices gets more and moretime critical. With computer systems becoming more and more complex, thecomplexity often comes with low efficiency regarding the requiredcommunication, when executing instructions.

SUMMARY

Various embodiments provide a method for processing an instruction by aprocessor as well as a computer system and a computer program productfor executing the method as described by the subject matter of theindependent claims. Advantageous embodiments are described in thedependent claims. Embodiments of the present invention can be freelycombined with each other if they are not mutually exclusive.

In one aspect, the disclosure relates to a method for processing aninstruction by a processor. The processor is operationally connected toone or more buses. The processor determines the instruction is to accessan address of an address space. The address space maps a memory andadditionally comprises a range of MMIO addresses. The method determinesthe address being accessed by the instruction is within the range ofMMIO addresses. The method generates, based on the determination thatthe address being accessed is within the range of MMIO addresses, afirst translation of the address being accessed to a bus identifieridentifying one of the buses and a bus address of a bus address space.The bus address space is assigned to the identified bus. Furthermore,the bus address resulting from the translation is assigned to a deviceaccessible via the identified bus. The method generates an entry in atranslation lookaside buffer. The generated entry enables a translationof the address being accessed to the bus identifier and bus addressresulting from the translation using the translation table. Based on theinstruction a request directed to the device is sent via the identifiedbus to the bus address resulting from the translation.

In a further aspect, the disclosure relates to a system comprising oneor more processors and a memory communicatively coupled to the one ormore processors. The one or more processors are operationally connectedto one or more buses. The computer system is configured to process aninstruction by a processor. The system determines the instruction is toaccess an address of an address space. The address space maps a memoryand in addition comprises a range of MMIO addresses. The processingcomprises determining the address being accessed by the instruction iswithin the range of MMIO addresses. The method generates, based on thedetermination that the address being accessed is within the range ofMMIO addresses, a first translation of the address being accessed to abus identifier identifying one of the buses and a bus address of a busaddress space. The bus address space assigned to the identified bus.Furthermore, the bus address resulting from the translation is assignedto a device accessible via the identified bus. The system generates anentry in a translation lookaside buffer. The generated entry enables atranslation of the address being accessed to the bus identifier and busaddress resulting from the translation using the translation table.Based on the instruction a request directed to the device is sent viathe identified bus to the bus address resulting from the translation.

In a further aspect, the disclosure relates to a computer programproduct. The computer program product comprises a computer-readablestorage medium which has machine executable program instructionsembodied therewith. The computer program product is configured toprocess an instruction by a processor. The computer program productdetermines the instruction is to access an address of an address space.The address space maps a memory and in addition comprises a range ofMMIO addresses. The computer program product determines the addressbeing accessed by the further instruction is within the range of MMIOaddresses. The computer program product generates, based on thedetermination that the address being accessed is within the range ofMMIO addresses, a first translation of the address being accessed to abus identifier identifying one of the buses and a bus address of a busaddress space. The bus address space is assigned to the identified bus.Furthermore, the bus address resulting from the translation is assignedto a device accessible via the identified bus. The computer programproduct generates an entry in a translation lookaside buffer. Thegenerated entry enables a translation of the address being accessed tothe bus identifier and bus address resulting from the translation usingthe translation table. Based on the further instruction a requestdirected to the device is sent via the identified bus to the bus addressresulting from the translation.

The above summary is not intended to describe each illustratedembodiment or every implementation of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included in the present application are incorporated into,and form part of, the specification. They illustrate embodiments of thepresent disclosure and, along with the description, serve to explain theprinciples of the disclosure. The drawings are only illustrative ofcertain embodiments and do not limit the disclosure.

FIG. 1 depicts a block diagram of an example computer system, inaccordance with embodiments of the present disclosure.

FIG. 2 depicts a schematic diagram of an example address structure, inaccordance with embodiments of the present disclosure.

FIG. 3 depicts a schematic flow diagram of an example method forprocessing an instruction accessing an address of an address space, inaccordance with embodiments of the present disclosure.

FIG. 4 depicts a schematic flow diagram of an example method forprocessing an instruction accessing an address of an address space usinga TLB, in accordance with embodiments of the present disclosure.

FIG. 5 depicts a schematic flow diagram of an exemplary method forprocessing an instruction accessing a partition absolute address, inaccordance with embodiments of the present disclosure.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

The descriptions of the various embodiments of the present invention arebeing presented for purposes of illustration, but are not intended to beexhaustive or limited to the embodiments disclosed. Many modificationsand variations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

A MMIO (Memory Mapped Input/Output) address is an address used byprocessor instructions to read or write on a bus, such as e.g., a PCIe(Peripheral Component Interconnect Express) bus, in a memory mapped way.As used herein, memory mapped means from that the processor instructionsuse the same addressing scheme as used for accessing physical mainmemory. For example, an instruction with store-to-memory characteristicsmay send the data referred to through a PCIe bus to a PCIe deviceinstead of storing the respective data to memory, and an instructionwith load characteristics may request a device, like e.g., an I/Odevice, through the PCIe bus to respond with the requested data insteadof reading the data from memory.

Embodiments of the present disclosure discussed herein are presentedwhere the buses are PCIe buses, the device is a PCIe device, and the busaddress is a PCIe bus address. However, the present disclosure shouldnot be read as limited to such and may be used with or adapted toalternate buses, devices, and bus addresses.

PCIe addresses are generally organized in a hierarchical addressingstructure. A BAR (Base Address Register) in PCIe defines a start addressand length of an address space assigned to a component, e.g., afunction, a switch, a bus, a PCIe bus unit, etc. Firmware typicallyinitializes the addressing structure by executing a bus walk, i.e.systematically scanning or “walking through” the components accessiblevia the buses comprised by the computer system.

Some embodiments of the present disclosure have the beneficial effect ofsimplifying and speeding up device identification, and moreparticularly, identification of a bus and bus address assigned to arespective device. A translation table may provide a simple approach totranslate a MMIO address to a bus identifier and a bus address. Thedevice may for example be an input/output (I/O) device or a memorydevice. Embodiments may introduce an MMIO range between a MemoryManagement Unit (MMU) of a processor and a dynamic address translation(DAT) table of an operating system on one side and one or more PCIe BaseAddress Registers (PCIe BAR) on the other side.

In addition to the translation table, a translation lookaside buffer(TLB) is provided. The TLB buffers the translation results oftranslations executed using the translation table. Using such a buffermay have the beneficial effect that translation may be executed on thehardware level without involving firmware. Thus, identifyingtranslations using a buffer may be more efficient than using atranslation table each time. In particular, if the same MMIO address isto be translated repeatedly, using the buffer, buffering priortranslation results may be efficient.

FIG. 1 depicts a computer system 100 suited for implementing a methodfor processing an instruction accessing a MMIO address and translatingthe MMIO address in order to determine a bus identifier and a busaddress to which a request is to be send based on the instructionprocessed. It will be appreciated that the methods described herein areat least partly non-interactive, and automated by way of computerizedsystems, such as servers or embedded systems. In example embodimentsthough, the methods described herein may be implemented in a (partly)interactive system. These methods may further be implemented in software(e.g. instructions 112), firmware (including basic input output system(BIOS) 122), hardware (e.g., processor 105), or a combination thereof.In example embodiments, the methods described herein are implemented insoftware, as an executable program, and are executed by a special orgeneral-purpose digital computer, such as a personal computer,workstation, minicomputer, or mainframe computer. The most generalcomputer system 100 therefore includes a general-purpose computer 101.

In example embodiments, in terms of hardware architecture, as shown inFIG. 1, the computer 101 includes a processor 105, memory (e.g., mainmemory) 110 coupled to a memory controller 115, and one or more inputand/or output (I/O) devices (or peripherals) 10 and 145 that arecommunicatively coupled via a local input/output controller 135. Theinput/output controller 135 may be, but is not limited to, one or morebuses or other wired or wireless connections, as is known in the art.The input/output controller 135 may have additional elements, which areomitted for simplicity, such as controllers, buffers (caches), drivers,repeaters, and receivers, to enable communications. Further, the localinterface may include address, control, and/or data connections toenable appropriate communications among the aforementioned components.The I/O devices 10 and 145 may e.g., comprise any portable storagedevice 10 or stationary storage device 145.

The processor 105 is a hardware device for executing software,particularly that stored in memory 110. The processor 105 may be anycustom made or commercially available processor, a central processingunit (CPU), an auxiliary processor among several processors associatedwith the computer 101, a semiconductor based microprocessor (in the formof a microchip or chip set), a macroprocessor, or generally any devicefor executing software instructions.

The memory 110 may include any one or combination of volatile memoryelements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM,etc.)) and nonvolatile memory elements (e.g., ROM, erasable programmableread only memory (EPROM), electronically erasable programmable read onlymemory (EEPROM), programmable read only memory (PROM). Note that thememory 110 may have a distributed architecture, where various componentsare situated remote from one another, but may be accessed by theprocessor 105.

The software in memory 110 may include one or more separate programs,each of which comprises an ordered listing of executable instructionsfor implementing logical functions, notably functions involved inembodiments of this disclosure. In the example of FIG. 1, software inthe memory 110 includes instructions 112.

The software in memory 110 may also include a suitable operating system(OS) 111. The OS 111 essentially controls the execution of othercomputer programs, such as instructions 112 for implementing methods asdescribed herein.

The methods described herein may be in the form of a source program,executable program (object code), script, or any other entity comprisinga set of instructions to be performed. When being provided as a sourceprogram, then the respective program needs to be translated via acompiler, assembler, interpreter, or the like, which may or may not beincluded within the memory 110, so as to operate properly in connectionwith the OS 111. Furthermore, the methods may be written as anobject-oriented programming language, which has classes of data andmethods, or a procedure programming language, which has routines,subroutines, and/or functions.

In example embodiments, a conventional keyboard 150 and mouse 155 mayalso be coupled to the input/output controller 135. Other output devicessuch as the I/O devices 145 may include input devices, for example butnot limited to a printer, a scanner, microphone, and the like. Finally,the I/O devices 10 and 145 may further include devices that communicateboth inputs and outputs, for instance but not limited to, a networkinterface card (NIC) or modulator/demodulator (for accessing otherfiles, devices, systems, or a network), a radio frequency (RF) or othertransceiver, a telephonic interface, a bridge, a router, and the like.The I/O devices 10 and 145 may be any generalized cryptographic card orsmart card known in the art. The system 100 may further include adisplay controller 125 coupled to a display 130. In example embodiments,the system 100 may further include a network interface for coupling to anetwork 165. The network 165 may be an IP-based network forcommunication between the computer 101 and any external server, clientand the like via a broadband or other connection. The network 165transmits and receives data between the computer 101 and externalsystems 30. In example embodiments, network 165 may be a managed IPnetwork administered by a service provider. The network 165 may beimplemented in a wireless fashion, e.g., using wireless protocols andtechnologies, such as WiFi, WiMax, etc. The network 165 may also be apacket-switched network such as a local area network, wide area network,metropolitan area network, Internet network, or other similar type ofnetwork environment. The network 165 may be a fixed wireless network, awireless local area network (LAN), a wireless wide area network (WAN) apersonal area network (PAN), a virtual private network (VPN), intranetor other suitable network system and includes equipment for receivingand transmitting signals.

If the computer 101 is a PC, workstation, intelligent device or thelike, the software in the memory 110 may further include a basic inputoutput system (BIOS) 122. The BIOS is a set of essential softwareroutines that initialize and test hardware at startup, start the OS 111,and support the transfer of data among the hardware devices. The BIOS isstored in ROM so that the BIOS may be executed when the computer 101 isactivated.

When the computer 101 is in operation, the processor 105 is configuredto execute instructions 112 stored within the memory 110, to communicatedata to and from the memory 110, and to generally control operations ofthe computer 101 pursuant to the software. The methods described hereinand the OS 111, in whole or in part, but typically the latter, are readby the processor 105, possibly buffered within the processor 105, andthen executed.

When the systems and methods described herein are implemented ininstructions 112, as is shown in FIG. 1, the methods may be stored onany computer readable medium, such as storage 120, for use by or inconnection with any computer related system or method. The storage 120may comprise a disk storage such as HDD storage.

FIG. 2 depicts a schematic diagram illustrating an example addressstructure. An address space may be provided in form of a partitionabsolute address space 203 assigned to a partition. When the partitionissues an instruction, the instruction may access a virtual address 200.The virtual address may be translated using a Memory Management Unit(MMU) and/or Dynamic Address Translation (DAT) table 202 to a partitionabsolute address of the partition absolute address space 203. Forexample, the virtual address may be converted by DAT to a real addressand then by prefixing to an absolute address. The partition absoluteaddress space 203 may comprise a range of absolute addresses mapping amemory. The respective range may extend from a lower limit, e.g., 0, toan upper limit MLS. In addition, the partition absolute address space203 comprises a range of MMIO addresses extending from a lower limit,i.e. start like e.g., 0xF0 . . . , to an upper limit, i.e. end likee.g., 0xFFFFFFFFFFFFFFFF. The absolute address accessed by theinstruction may either be comprised by the memory mapped range 204 or bythe MMIO range 206 of absolute partition addresses. The MMIO range 206may cover BARs of one or more PCIe bus units (PBU) 210 and 208. Forexample, absolute addresses 0xF1 . . . to 0xF2 . . . may be addressesfor accessing a first PBU0 BAR 208, while other absolute partitionaddresses 0xF0 . . . to 0xF1 . . . may be addresses for accessing afurther PBU1 BAR 210. The PBUs may comprise one or more buses. Thus, thePBU Bars may comprise one or more bus BARs. For example, PBU0 BAR 208may comprise Bus0 Bar 212. Bus0 Bar 212 may e.g., comprise Switch0 Port1BAR 214 which is accessible via a range of absolute partition addresses,like e.g., 0xF10 . . . to 0xF11 . . . . Switch0 Port1 BAR 214 maycomprise one or more function BARs, like e.g., Func 1 BAR 216 and Func 2BAR 218, each of which is addressable via range of absolute partitionaddresses comprised by the MMIO range 206. Func 1 BAR 216 may e.g., beaddressable using absolute partition addresses 0xF1010 . . . to 0xF1011. . . and Func 2 BAR 218 may e.g., be addressable using absolutepartition addresses 0xF1011 . . . and 0xF1012 . . . . Thus, a MMIOaddress comprised by MMIO range 206 may be translated to a busidentifier identifying a bus, like e.g., Bus0, and a bus address, e.g.,a PCIe bus address. The PCIe bus address may identify a PCIe bus addressof a PCIe bus address space assigned to the identified bus, e.g., Bus0.

FIG. 3 depicts a schematic flow diagram of an example method 300 forprocessing an instruction accessing an address of an address space. At310, a processor receives the instruction accessing an address of anaddress space. The address can be a partition absolute address (PAA) 330of a partition absolute address space. PAA 330 may comprise a firstsection providing a MMIO index (MMIO_Idx) 332, which may be used toidentify an entry 338 of the translation table providing a busidentifier Hardware Request Routing Address (HRRA) 340, and a remainingportion 334.

At 312, in order to identify entry 308 of the translation table, theprocessor multiplies the MMIO_Idx with a byte offset. The byte offsetmay e.g., be 16 bytes (where the *16 in FIG. 3 represents multiplicationby 16).

At 314, the processor adds a MMIO table base address. The result may bethe address of translation table entry 338. Entry 338 may comprise a busidentifier HRRA 340 identifying a bus. HRRA 340 may e.g., identify adrawer, cluster, port etc. The entry 338 may further comprise a baseaddress (MMIO_base) 344 of the identified bus, i.e. a lower limit of thebus address space assigned to the identified bus, as well as a limitaddress (MMIO_limit) 342 of the identified bus, i.e. an upper limit ofthe bus address space assigned to the identified bus.

At 316, the remaining portion 334 of PAA 330 may e.g., be added toMMIO_base by the processor.

At 318, the processor checks whether the resulting bus address is withinthe bus address space assigned to the identified bus. In other words,the processor checks whether the result is smaller than MMIO_limit 342.In response to determining that the result is not smaller, the busaddress is erroneous and lies without the bus address space assigned tothe identified bus and e.g., a machine check may be performed at 320. Inresponse to determining that the result is smaller, the bus address is avalid bus address of the bus address space assigned to the identifiedbus and a request is forwarded to the PBU identified by HRRA 340 at 322.More precisely, a request directed to a device accessible via theidentified bus is sent via the identified bus to the bus address at 322.

At 324, a TLB entry comprising the result of the translation above isgenerated. The TLB entry can comprise the MMIO_Idx 332, the HRRA 340,the MMIO_limit 342, and the MMIO_base 344. The TLB entry can comprisethe translation of the PAA 330. In some embodiments, a partition ID of apartition which issued the instruction can be assigned to the TLB entry.

FIG. 4 depicts a schematic flow diagram of an example method 400 forprocessing an instruction accessing an address of an address space usinga TLB. At 410, a processor receives the instruction accessing an addressof an address space. The address can be e.g., the MMIO address of FIG. 3or a similar address.

At 412, the processor compares the MMIO_Idx (such as MMIO_Idx 332 ofFIG. 3) with the MMIO_Idx values of the entries contained within theTLB. This can comprise checking whether the TLB contains an entry with aMMIO_Idx identical to the MMIO_Idx of the instruction. In someembodiments, this can also comprise checking whether a partition ID ofthe partition which issued the instruction is identical with a partitionID assigned to a TLB entry. At 414, the processor determines theMMIO_Idx values match.

In order to determine the bus address addressed by the address of theinstruction, analogously to FIG. 3, the remaining portion of the address(e.g., 334 the address in FIG. 3) may e.g., be added to a MMIO_base at416.

At 418, the processor checks whether the resulting bus address is withinthe bus address space assigned to the identified bus, similarly tooperation 318 of FIG. 3. In other words, it is checked whether theresult is smaller than MMIO_limit. In case the result is not smaller,the bus address is erroneous and lies without the bus address spaceassigned to the identified bus and e.g., a machine check may beperformed at 420. In case the result is smaller, the bus address is avalid bus address of the bus address space assigned to the identifiedbus and a request is forwarded to the PBU identified by HRRA at 422.According to some embodiments, the request may be aggregated in anaggregation buffer and the aggregated requests may be forwarded togetherusing write combine.

FIG. 5 depicts a schematic flow diagram of an example method 599 forprocessing an instruction accessing a partition absolute address. At500, the partition absolute address is accessed by the instruction. At502, it is checked whether the PAA is an MMIO address (MMIOA), i.e.whether the PAA is within the MMIO range. If this is not the case, thePAA may be an address mapping an address of a memory. Thus, at 504, thememory is accessed. If it is within the MMIO range, it is checked at 506whether a TLB miss occurs, when querying the TLB for an entry providinga translation of the PAA (i.e. there is no entry in the TLBcorresponding to the PAA). If no TLB miss occurs, i.e. if the TLBprovides a translation of the PAA, the MMIOA provided in form of the PAAis translated using the TLB at 508 in order to provide a bus identifierand a bus address. If a TLB miss occurs, the MMIOA is translated at 510using the translation table (TT) in order to provide the bus identifierand the bus address. Furthermore, an entry of the TLB is generated at512 using the results of 510. At 514, a request is sent to thetranslation result of 508 or 510, respectively.

According to some embodiments, the TLB used for the MMIO addresses maybuffer translations of MMIO addresses to explicit physical targetaddresses plus an offset within the respective physical target. Thephysical target may e.g., be a PHB (PCIe host bridge) connecting theCPU/memory domain of a computer system to a PCIe bus. The TLB used forthe MMIO addresses may further buffer information if write combiningshould be executed using an aggregation buffer or if the data to bewritten should rather be forwarded right away to the PCIe device.

According to some embodiments, the processor determines whether the busaddress resulting from the translation lies within the range of the busaddress space assigned to the bus identified by the bus identifierresulting from the translation. According to some embodiments, in casethe bus address resulting from the translation does not lie within therange of the bus address space assigned to the bus identified by the busidentifier resulting from the translation, the processor prevents that arequest based on the instruction is sent. Embodiments may have thebeneficial effect of ensuring that the bus address resulting from thetranslation lies within the range of the bus address space assigned tothe bus identified by the bus identifier resulting from the translation.In these embodiments, only if this is the case, a request directed tothe device is sent via the identified bus to the bus address. Otherwise,the MMIO address used may be erroneous. Thus, using an erroneous MMIOaddress is prevented which otherwise could result in sending a requestto a wrong device.

According to some embodiments, the translation lookaside buffercomprises identifiers identifying an upper and a lower limit of the busaddress space assigned to the bus identified by the bus identifierresulting from the translation. The identifiers identifying the upperand the lower limit are used for determining whether the resulting busaddress lies within the range defined by the upper and the lower limit.Embodiments may have the beneficial effect of providing an efficientapproach using the translation lookaside buffer to determine whether thebus address resulting from the translation lies within the range of thebus address space assigned to the bus identified by the bus identifierresulting from the translation.

According to some embodiments, the translation table comprisesidentifiers identifying an upper and a lower limit of the bus addressspace assigned to the bus identified by the bus identifier resultingfrom the translation. The identifiers identifying the upper and thelower limit are used for determining whether the resulting bus addresslies within the range defined by the upper and a lower limit.Embodiments may have the beneficial effect providing an efficientapproach using the translation table to determine whether the busaddress resulting from the translation lies within the range of the busaddress space assigned to the bus identified by the bus identifierresulting from the translation.

According to some embodiments, the address being accessed by aninstruction comprises a first section encoding an identifier foridentifying the bus identifier. According to some embodiments, theidentifier for identifying the bus identifier comprises an entryidentifier identifying an entry in the translation lookaside buffer. Therespective entry to be identified is assigned with an equal entryidentifier. A translation lookaside buffer hit results from finding theentry identifier provided by the address to be accessed in an entry inthe translation lookaside buffer assigned with an equal entryidentifier. Embodiments may have the beneficial effect of efficientlyproviding the bus identifier. According to some embodiments, atranslation lookaside buffer miss results from not finding the entryidentifier provided by the address to be accessed in an entry in thetranslation lookaside buffer assigned with an equal entry identifier.

According to some embodiments, the address comprises a second sectionencoding the bus address of the bus address space assigned to the deviceaccessible via the bus identified by the first section.

According to some embodiments, the identifier for identifying the busidentifier comprises an entry identifier identifying an entry in thetranslation table providing the bus identifier. Embodiments may have thebeneficial effect of efficiently providing the bus identifier.

According to some embodiments, in case the translation lookaside bufferhas no remaining capacity for adding additional entries, the generatingof an entry in the translation lookaside buffer comprises replacing anexisting entry of the translation lookaside buffer with the entry to begenerated. Embodiments may have the beneficial effect that by limitingthe capacity of the translation lookaside buffer, only a limited numberof previous translation results may be buffered. Thus, it may be ensuredthat searching the buffer may be fast.

According to some embodiments, entries comprised by the translationlookaside buffer can be each assigned to individual partitions. Theaddress space comprising the address accessed by the instruction can bean absolute partition address space assigned to a partition and theinstruction can be an instruction issued by the respective partition.Embodiments may have the beneficial effect of providing partitionindividual entries. Thus, e.g., different access rights may be definedfor different partitions.

According to some embodiments, the translation table can be assigned tothe partition and the instruction can be an instruction issued by thepartition. Embodiments may have the beneficial effect of providingpartition individual translation tables. Thus, e.g., different accessrights may be defined for different partitions.

According to some embodiments, the processor can be provided with apartition identifier identifying the partition issuing the instruction.Embodiments may have the beneficial effect of that the processor isenabled to identify which partition is issuing the instruction and thustrying to access the MMIO address and via the MMIO address, theunderlying bus and bus address. The partition identifier may e.g., beused to identify an entry of the translation lookaside buffer and/or atranslation table assigned to the respective partition.

According to some embodiments, the translation table providestranslations for each address of the MMIO range and to each address ofthe MMIO range an access indicator is assigned. The access indicatorindicates, whether an access to the respective address of the MMIO rangeis allowed. The processor uses the access indicator to check whether theaccess the address being accessed by the instruction is allowed. In casethe access is not allowed, the processor prevents that a request basedon the instruction is sent. Embodiments may have the beneficial effectthat all MMIO addresses are visible for a partition, but that using theaccess indicator access rights may be defined restricting the accessrights of the respective partition.

According to some embodiments, in order to prevent that a request basedon the instruction is sent, when the access is not allowed, theprocessor may interrupt the processing of the instruction and a pendinginterrupt may be generated or the instruction may be ignored by theprocessor. Furthermore, an exception may be indicated by the processor.

According to some embodiments, the translation table only providestranslations for addresses of the MMIO range which the partition isallowed to access. In case translation table provides no translation forthe address being accessed by the instruction, no request based on theinstruction is sent. Embodiments may have the beneficial effect thattranslations are only provided for MMIO address which the partition isallowed to access. For other MMIO addresses no translations areprovided. Thus, the processor is unable to send a request directed tothe device based on an instruction trying to access such an MMIOaddress.

According to some embodiments, write combine is enabled for theaddresses of the MMIO range using an aggregation buffer for aggregatingrequests. As used herein, write combine refers to a computer bustechnique for allowing data to be combined and temporarily stored in theaggregation buffer to be released together later in burst mode.Embodiments may have the beneficial effect of providing an efficientapproach to execute a plurality of write instructions.

The aggregation buffer may collect consecutive stores on incrementingaddresses. In some embodiments, a number 2^(N) boundaries may apply.Possible aggregation approaches may comprise: when a store operation isnon-aggregating, the written bytes of the aggregation buffer may be sentto the PBU indicated by the translation performed using the TLB. When anexisting PCIe instruction is issued, firmware may push out the bufferbefore executing the instruction.

According to some embodiments, for each combination of bus identifierand bus address, two addresses are provided in the MMIO range. A firstaddress is provided for executing a write through to the respective busaddress and a second address is provided for executing a write combineto the respective bus address. Embodiments may have the beneficialeffect of efficiently implementing a write through mode as well as aparallel write combine mode. Depending on the MMIO address accessed, itmay be chosen between the write through mode and the write combine mode.

For example, a write combining enabled bit may be added to the MMIOaddress range for controlling aggregation/ordering. For example, anunused bit may be considered, e.g., bit 1. Thus, each bus address may beseen as mapped twice into the MMIO address range, once with writecombined ordering and once with write through ordering.

According to some embodiments, the bus identifier comprises one or moreof the following for identifying the bus: a node number, a chip number,a bus unit number, or a bus number. Embodiments may have the beneficialeffect of providing an efficient bus identifier.

According to some embodiments, an MMIO capability bit is added to aquery function for an operating system (OS) to identify if the systemsupports the embodiments of the present disclosure discussed herein. Ifthe capability bit is set, the firmware may configure BAR spaces in PCIedevices to contain proper physical addresses (PAs) before signaling hotplug to the OS. Furthermore, the OS may be configured to actually usethese PAs. In some embodiments, the TLB may be invisible to the OS.

According to some embodiments, the computer system further is configuredto execute any of the embodiments of the method for processing theinstruction by the processor as described herein.

It is understood that one or more of the aforementioned embodiments ofthe invention may be combined as long as the combined embodiments arenot mutually exclusive. Ordinal numbers, like e.g., ‘first’ and‘second’, are used herein to indicate different element assigned withthe same name, but do not necessarily establish any order of therespective elements.

The present invention may be a system, a method, and/or a computerprogram product at any possible technical detail level of integration.The computer program product may include a computer readable storagemedium (or media) having computer readable program instructions thereonfor causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, configuration data for integrated circuitry, oreither source code or object code written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Smalltalk, C++, or the like, and procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The computer readable program instructions may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider). In some embodiments, electronic circuitry including,for example, programmable logic circuitry, field-programmable gatearrays (FPGA), or programmable logic arrays (PLA) may execute thecomputer readable program instructions by utilizing state information ofthe computer readable program instructions to personalize the electroniccircuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

What is claimed is:
 1. A method for processing an instruction by aprocessor, wherein the processor is operationally connected to one ormore buses, wherein the method comprises: determining the instruction isto access an address of an address space, wherein the address space mapsa memory, and wherein the address space additionally comprises a rangeof Memory Mapped Input/Output (MMIO) addresses; determining the addressbeing accessed by the instruction is within the range of MMIO addresses;generating, based on the determination that the address being accessedis within the range of MMIO addresses, a first translation of theaddress being accessed to a bus identifier identifying one of the busesand a bus address of a bus address space assigned to the identified bususing a translation table, wherein the bus address resulting from thetranslation is assigned to a device accessible via the identified bus;generating an entry in a translation lookaside buffer, wherein thegenerated entry enables a translation of the address being accessed tothe bus identifier and bus address resulting from the translation usingthe translation table; and sending, based on the instruction, a requestdirected to the device via the identified bus to the bus addressresulting from the first translation.
 2. The method of claim 1 furthercomprising: receiving a second instruction; determining the secondinstruction is to access the address of the address space; generating,based on the determination that the address being accessed is within therange of MMIO addresses, a second translation of the address beingaccessed to a bus identifier identifying one of the buses and a busaddress of a bus address space assigned to the identified bus using thetranslation lookaside buffer; and sending, based on the secondinstruction, a second request directed to the device via the identifiedbus to the bus address resulting from the second translation.
 3. Themethod of claim 2, wherein the processor determines, whether the busaddress resulting from the second translation lies within the range ofthe bus address space assigned to the bus identified by the busidentifier resulting from the second translation.
 4. The method of claim3, wherein the translation lookaside buffer contains identifiersidentifying an upper limit and a lower limit of the bus address spaceassigned to the bus identified by the bus identifier resulting from thesecond translation for determining whether the resulting bus addresslies within the range defined by the upper limit and the lower limit. 5.The method of claim 3, wherein the translation table comprisesidentifiers identifying an upper limit and a lower limit of the busaddress space assigned to the bus identified by the bus identifierresulting from the first translation for determining whether theresulting bus address lies within the range defined by the upper limitand the lower limit.
 6. The method of claim 2, wherein the address beingaccessed by the instruction comprises a first section encoding anidentifier for identifying the bus identifier.
 7. The method of claim 6,wherein the identifier for identifying the bus identifier comprises anentry identifier identifying an entry in the translation lookasidebuffer, wherein the respective entry to be identified is assigned withan equal entry identifier and wherein a translation lookaside buffer hitresults from finding the entry identifier provided by the address to beaccessed in an entry in the translation lookaside buffer assigned withan equal entry identifier.
 8. The method of claim 7, wherein atranslation lookaside buffer miss results from finding the entryidentifier provided by the address to be accessed to not match any entryin the translation lookaside buffer assigned with an equal entryidentifier.
 9. The method of claim 6, wherein the address comprises asecond section encoding the bus address of the bus address spaceassigned to the device accessible via the bus identified by the firstsection.
 10. The method of claim 6, wherein the identifier foridentifying the bus identifier comprises an entry identifier identifyingan entry in the translation table providing the bus identifier.
 11. Themethod of claim 1, wherein the translation lookaside buffer has noremaining capacity for adding additional entries, and wherein thegenerating of the entry in the translation lookaside buffer comprisesreplacing an existing entry of the translation lookaside buffer with theentry to be generated.
 12. The method of claim 1, wherein the buses arePCIe (Peripheral Component Interconnect Express) buses, wherein thedevice is a PCIe device and wherein the bus address is a PCIe busaddress.
 13. The method of claim 1, wherein entries comprised by thetranslation lookaside buffer are each assigned to individual partitions,wherein the address space comprising the address accessed by theinstruction is an absolute partition address space assigned to apartition, and wherein the instruction is an instruction issued by therespective partition.
 14. The method of claim 1, wherein the processoris provided with a partition identifier identifying the partitionissuing the instruction.
 15. The method of claim 1, wherein thetranslation table contains translations for each address of the MMIOrange, wherein each address of the MMIO range has an assigned accessindicator which indicates whether an access to the respective address ofthe MMIO range is allowed.
 16. The method of claim 1, wherein thetranslation table only contains translations for addresses of the MMIOrange the partition is allowed to access.
 17. The method of claim 1,wherein write combine is enabled for the addresses of the MMIO rangeusing an aggregation buffer for aggregating requests.
 18. The method ofclaim 17, wherein for each combination of bus identifier and bus addresstwo addresses are provided in the MMIO range, wherein a first one of thetwo addresses is provided for executing a write through to therespective bus address and a second one of the two addresses is providedfor executing a write combine to the respective bus address.
 19. Asystem for processing an instruction by a processor comprising: one ormore processors, wherein the one or more processors are operationallyconnected to one or more buses; and a memory communicatively coupled tothe one or more processors, wherein the memory comprises instructionswhich, when executed by the one or more processors, cause the one ormore processors to perform a method comprising: determining theinstruction is to access an address of an address space, wherein theaddress space maps a memory, and wherein the address space additionallycomprises a range of Memory Mapped Input/Output (MMIO) addresses;determining the address being accessed by the instruction is within therange of MMIO addresses; generating, based on the determination that theaddress being accessed is within the range of MMIO addresses, a firsttranslation of the address being accessed to a bus identifieridentifying one of the buses and a bus address of a bus address spaceassigned to the identified bus using a translation table, wherein thebus address resulting from the translation is assigned to a deviceaccessible via the identified bus; generating an entry in a translationlookaside buffer, wherein the generated entry enables a translation ofthe address being accessed to the bus identifier and bus addressresulting from the translation using the translation table; and sending,based on the instruction, a request directed to the device via theidentified bus to the bus address resulting from the first translation.20. A computer program product for processing an instruction by aprocessor, the computer program product comprising a computer readablestorage medium having machine executable program instructions embodiedtherewith, wherein the computer readable storage medium is not atransitory signal per se, the program instructions executable by acomputer to perform a method comprising: determining the instruction isto access an address of an address space, wherein the address space mapsa memory, and wherein the address space additionally comprises a rangeof Memory Mapped Input/Output (MMIO) addresses; determining the addressbeing accessed by the instruction is within the range of MMIO addresses;generating, based on the determination that the address being accessedis within the range of MMIO addresses, a first translation of theaddress being accessed to a bus identifier identifying one of the busesand a bus address of a bus address space assigned to the identified bususing a translation table, wherein the bus address resulting from thetranslation is assigned to a device accessible via the identified bus;generating an entry in a translation lookaside buffer, wherein thegenerated entry enables a translation of the address being accessed tothe bus identifier and bus address resulting from the translation usingthe translation table; and sending, based on the instruction, a requestdirected to the device via the identified bus to the bus addressresulting from the first translation.